(1) FieId of the invention
This invention relates to a process for producing a blown film of butene-1 polymer. More particularly, it relates to a process for producing a blown film superior in elasticity, elastic recovery, impact strength and the like.
(2) Description of the Related Art
Recently, demand for improvement of properties of film of butene-1 has been increased.
Hitherto, a process for producing polybutene sheet superior in elasticity and elastic recovery has been known which comprises further heat-treating a stretched polybutene at a specific temperature. (See. Japanese Patent Kokai No. 50-96671.)
However, this process is industrially disadvantageous because steps are complicated and troubles are apt to occur. Besides, the products are not satisfactory in elastic recovery. Therefore, there has been demanded a process for producing a polybutene sheet superior in elasticity and elastic recovery without heat treatment step.
A film comprising a blend of butene-1 copolymer, a low-density polyethylene and a polypropylene has been known. (See, Japanese Patent Kokoku No. 54-39859 and Japanese Patent Kokai No. 50-14741.) However, there has been no sufficient research on molding of a film comprising butene-1 polymer alone.